Gnatyshyna L. Stress-responsive molecular systems in freshwater mollusks under effect of environmental pollution.

Thesis is devoted to the study of molecular systems response to stress, and detoxification of xenobiotics in the bivalve (mussel Anodonta cygnea L.) and pulmonate (pond snail Lymnaea stagnalis) freshwater mollusks under the effect of inappropriate environmental and experimental (effect of pesticide clofentezine (Apollo), elevated temperature, ionizing radiation) conditions. Differences between the seasonal dynamic and (for mussel) responses on the effect of clofentizine (10 µg/L during 14 days) was shown for the mollusks from different areas. Hyperactivity of superoxide dismutase forms: cytosolic Cu,Zn-SOD in the mussel and mitochondrial Mn-SOD in the snail (more than 10 times higher), low redox index of glutathione (RI GSH reach values to 0,45 and 0,65 in polluted site compared in reference, p>0,05) and elevated protein carbonyls (PC) levels (to 4,0 and 5,5 times in bivalve and 2 times in pulmonate mollusks) were shown for the mollusks from polluted areas in autumn. In the mussels, the correlation between PC and superoxide anion levels (r=0,53, p<0,001) that was accompanied by caspase-3 activation (till 62 times) was shown. Clofentizine provoked the pro-oxidative changes in the tissues of both groups of mussels, but the response of GSH was different for the mussels from clean (increase by 329%) and polluted (decrease by 84%) area. In the snail, the effect of ionizing radiation (2mGy) provoked the elevation of Mn-SOD (by 63%) and GSH levels (by 34%), and the effect of elevated temperature (25оС during 4 days) caused the decrease of GSH (by 34%) and PC elevation (by 137%). For the metallothionein (MT), the signs of instability of molecular forms (particularly Cu-МТ-2 and МТ-4 kDa appearance), the leakage of metal-binding properties and decrease of the concentration were shown under the inappropriate conditions. These features were more expressed for Zn,Cu-MT of the mussel than for the Zn-MT of snail. The elevation of the part of apo-MT in comparison to metal-binding form of MT could promote the involving of MTs in the antioxidant defense. Inappropriate effects cause the signs of genotoxicity (elevated value of hemocytes with the nuclear abnormalities) and cytotoxicity (decrease of lysosome membrane stability). The persistent features of the mollusks from chronically polluted areas were elevated glutathione-S-transferase activity and vitellogenin-like protein levels (in mail mussel). Short-terming inappropriate effects caused the activation of ethoxiresorufin-O-deethilase (by two-five times) in the digestive gland of both mussel and snail. Snail possesses highest level of variability in the lactate dehydrogenize activity than the mussel. It was shown that cholineesterase activity in mollusks did not reflect the effect of toxic environment. The seasonal and local differences in the responses were proved by the applying of Factor analysis and Principal component analysis (with NIPALS algorithm). Main distinguishing features between the mollusks from different areas were selected by Classification trees building. The level of nuclear abnormalities and vitellogenin-like proteins distinguished the mussels from three sites independent from the season. The relation between the metal-binding activity of MT and PC level was proved.